The invention concerns acceleration engineering, and is especially addressed to induction accelerators. It has application as a commercial-type compact powerful accelerator of charged particles for the formation of relativistic beams of charged particles and for the system of many multi-component beams.
There is known an induction accelerator, which can be used as a device for the formation of singular electronic relativistic beams. See, Redinato L. “The advanced test accelerator (ATA), a 50-MeV, 10-kA Induction Linac”. IEEE Trans., NS-30, No 4, pp. 2970–2973, 1983. This device also is called the one-channel linear induction accelerator (OLINIAC). The OLINIAC composed of an injector block, a drive system, an output system, and a one-channel linear induction acceleration block. Its peculiarity is that the linear induction acceleration block is made in the form of a sequence of linearly connected acceleration sections. Each of the acceleration sections is made in the form of one or more magnetic inductors, which are enveloped by a conductive screen. Therein, one inner accelerative channel is axially placed within the inner parts of the conductive sleeves, which have corresponding apertures and slits. Channel electrodes are electrically connected with different parts of the conductive screens' inner parts, which are separated by the previously mentioned slits. Owing to this, an axially oriented accelerative electric field is generated between each pair of the channel electrodes.
Thus, the specific feature of the OLINIAC is that the acceleration space is made as a special break (slit) in the inner part of the conductive screen connected with the system of electrodes. That special break is accomplished in the form of the above-noted azimuthally oriented slits. The conductive screen, as a whole, shields the outside of the acceleration section from penetration of the vortex electric field generated inside. This means that the field exists within the inner bulk of the accelerative section only, including the above-mentioned slit in the inner part of the conductive screen. As a result the accelerative electric field is generated between the slit edges. The field is accelerative with respect to the charged particle beam. I other words, the azimuthally oriented inner slits plays a role of the acceleration space for the accelerating the charged particle beam.
The acceleration channel in the OLINIAC has a linear form. This is the main cause why this systems are called “linear”.
The large linear (longitudinal) dimensions, relatively low efficiency, limited functional potentialities, and limited range of the current strength of the accelerated beam are the basic shortcoming of the OLINIAC.
The large dimensions of the OLINIAC (e.g. 60–70 m length for the ATA class) are related to its moderate rates of linear acceleration. The typical energy rates of acceleration for the OLINIAC are ˜0.7–1.5 MeV/m. The acceleration rate for the ATA example described above is ˜0.75 MeV/m. As a result, the total length of the experimental ATA is ˜70 m. For a typical commercial system having an output energy ˜10 MeV, the total length would be ˜15 m. This causes a strong complication in the system's overall infrastructure and accommodation, radiation-protection means, and service system. As a result, commercial application of OLINIAC as a basic construction element for various types of commercial devices becomes economically unsuitable because of their excessive price.
The other shortcoming the OLINIAC is that, only one charged particle beam is accelerated at all stages of the acceleration process, i.e., the OLINIAC is the one-channel and, at the same time, one-beam system. However, a series of practical applications requires the formation of charged-particle beams with multi-component structure. For example, one such application is the electron beam for the two-stream superheterodyne free electron lasers (TSFEL), wherein two-velocity relativistic beams are used. Other examples include various systems for forming complex electron-ion or ion-ion beams. This means that the OLINIAC possesses limited functional possibilities with respect to its potential field of application.
It is well-known that the limited range of beam current strength in the OLINIAC is determined by a few simultaneous causes. It is well known that the limitations for the OLINIAC's range of beam current strength exist from the “down” as well as the “up”.
Three main causes for the limited range of beam current strength can be found. The first cause is connected to design and physical limitations characteristic for the chosen type of charged particle injectors. The greater is the beam current the more limited the range of beam current strength becomes. These limitations may be classified as the “limitations from the up”.
The second cause is connected to “limitations from the down”, which is connected with lower level of its efficiency in the case when the beam current magnitude is too low. The OLINIAC's main power losses Plos, which are related to the losses on remagnetization of the inductor magnetic cores, determine the OLINIAC's efficiency. These losses depend mainly on the core material and do not practically depend on current beam strength. On the other hand, the useful power Pus is the power that the beam obtains during the acceleration process. In contrast to the main power losses, the useful power depends strongly on beam current. As it is widely known, the particle efficiency ηp of the acceleration process is determined as a ratio of the useful power Pus to the total power                               η          p                =                                            P              us                                                      P                us                            +                              P                los                                              .                                    (        1        )            
This means that the main method of the efficiency increasing in this case is to increase the beam current. As experience shows, the power of losses became approximately equal to the useful power when the current beam ˜1 kA. Owing to this, the modern, high efficiency OLINIACs are characterized by a beam current ≧1 kA. The beam current for the above mentioned ATA is 10 kA.
Thus, the peculiar “limitation from the down” exists for the OLINIAC beam current. However, many practical applications require acceleration of beams of tens-hundreds of Amperes. At the same time, these applications simultaneously require high efficiency of the acceleration process. The OLINIAC does not satisfy these requirements.
The third cause of the current limitation is connected with inclination of the high current beams to excitation of the beam instabilities. Therein, the probability of instability excitation increases with increasing beam current density.
The fourth cause of the current limitation is related to the phenomenon of beam critical current. The critical current is a maximal current beam which can pass through the given accelerative channel. As a result, the formation and the acceleration of electron and ion beams, which are characterized by current of a few hundred kA and more, becomes a complicated technological problem in the case of OLINIAC.
Induction accelerators, called multi-channel induction accelerators (MIAC), may be used for formation of relativistic charged particle beams and systems of charged particle beams. Two versions of MIACs are known. Including, the multi-channel linear induction accelerator (MLINIAC) [V. V. Kulish and A. C. Melnyk. Multi-channel Linear Induction Accelerator, U.S. Pat. No. 6,653,640 B2, Date of patent Nov. 25, 2003] and the undulative EH-Accelerator [V. V. Kulish et. al. EH-accelerator, U.S. Pat. No. 6,433,494 B1, Date of patent Aug. 13, 2001; V. V. Kulish. Hierarchical methods. V. II, Undulative electromagnetic systems. Kluwer Academic Publishers, Boston/Dordrecht/London, 2002]. The latter also is called the multi-channel undulative induction accelerator (MUNIAC).
The MIAC consists of an injector block, a drive system, an output system, and a multi-channel induction accelerative block. For this system, the multi-channel induction acceleration block is formed as an aggregate of separate one-channel linear induction acceleration blocks, including those that are placed parallel with one another like those used in the OLINIAC. Like the OLINIAC, each one-channel linear induction acceleration block is formed as a sequence of linearly connected acceleration sections. Therein, each one-channel linear induction accelerative block contains only one inner accelerative channel. For example, all channels are placed axially within the inner parts of the conductive screens that have the inner slits. As with the OLINIAC, these slits play a role of accelerative spaces for the charged particle beams. Each inner channel electrode pair is electrically connected with corresponding inner parts of the conductive screens that are divided by the slit.
The MLINIAC differs from the MUNIAC in its block of output systems. In the case of MLINIAC this block is formed as an aggregate of partial outlet devices that are connected with the linear inner accelerative channels. These partial outlet devices may be the diaphragms, which separate the working volume vacuum from outside atmosphere, various control systems, which direct the beams in a chosen direction, compression or decompression systems, etc. These partial outlet devices also may be systems for merging together different partial beams of charged particles consisting of the same kind of particles as well as of a different particles, including, electrons and positive and negative ions.
In contrast to the MLINIAC, at least some of the MUNIAC's partial output devices are made in the form of turning systems, which connect outputs of one inner accelerative channels with inputs of other inner channels. Those inputs connected with injectors and those for expelling the accelerated particle beams are exceptions from this rule. Thus, each complete (i.e., continuous) acceleration channel in the MUNIAC represents by itself a sequence of linear inner accelerative channel and the channels within the turning systems, where beams turn at a 180° angle every time. This gives the accelerative charged particle beam an undulative-like form. In this connection the systems of this class are referred to as undulative.
Also known the MIAC with a mixed design of output systems.
Thus, the common feature of the MLINIAC and MUNIAC is that both contain the multi-channel accelerative blocks with inner accelerative channels. These blocks are formed as an aggregate of one-channel linear induction acceleration blocks, including those that are oriented parallel to one another. The dissimilarities are the designs' block of output systems.
These designs are not always competitors and each has optimal applications. For instance, the most promising MLINIAC application involves different types of especially powerful devices destined for generation relativistic charged particle beams, including those consisting of charged particles of different kind. In commercial applications, the beams are usually characterized by relatively low magnitudes of energy (not higher than 10 MeV) and very high magnitudes of total current including all beam components (tens–hundreds kA). The main merit of the MUNIAC is its relative compactness. For instance, using the MUNIAC design scheme with five turns, the total length of the above-described ATA-type OLINIAC can be reduced from the ˜70 m to ˜13 m. With this system, the total beam current could be increased, in principle, for a few times owing to application of the multi-channel design scheme. On the other hand, the MUNIAC design turns out to be too complicated in the case of forming complex beams consist of charged particles of different charge. Beside that, the MLINIAC-design has advantages over the MUNIAC in commercial cases when the beam energy does not exceed ˜5 MeV. Thus, the multi-channel induction accelerator (MIAC) partially solves problems characteristic of the OLINIAC. However, other problems are not satisfactory solved. Namely, the MIAC design is heavy. This can be explained by the increased total mass of the inductor magnetic cores used. The result is that the MIAC are very expensive. Apart from that, they have relatively low efficiency like the OLINIAC,.